The conventional catalytic converter for internal combustion engine exhaust utilizes a polycelluler ceramic monolith core on the cell surfaces of which is deposited a catalyst which aids in the conversion of pollutants contained in the exhaust, such as, carbon monoxide, nitrogen oxides (NO.sub.x), unburned hydrocarbons, etc. to carbon dioxide, nitrogen, and water. More recently, catalytic converters have been formed of metal which are less expensive and easier to manufacture. The latter may be electrically heated to elevate the temperature of the catalyst prior to contact with "cold exhaust" at start-up to effect substantial removal of pollutants which would otherwise escape to the atmosphere until the catalyst achieved a temperature, e.g., 500 to 700 degrees F., sufficient to promote oxidation or, in some cases, reduction of pollutant materials.
Catalytic converters formed of corrugated thin metal strips are known. See U.S. Pat. No. 4,711,009 to Richard C. Cornelison et al, dated 8 Dec. 1987 the disclosure of which is incorporated herein by reference. Electrically heated catalytic converters are also known. See the U.S. Pat. Nos. To Kitzner 3,768,982 and 3,770,389 each dated 30 Oct. 1973. The present invention is concerned with an improved structure for fabricating a catalytic converter body of corrugated thin metal strips and which converters are readily adapted to be electrically heatable. A process for corrugating, coating and applying catalyst to thin metal strips is disclosed in the aforesaid U.S. Pat. No. 4,711,009. The improved structure utilizes a corrugated thin metal (preferably a stainless steel) strip which is overfolded once (as distinct from accordion folded) and wherein a metal bar or rod of circular, square, rectangular or other polygonal cross-sectional configuration is secured, e.g. welded, to the overfolded strip along the fold line to form a core member. The member bar or rod has a length greater than the width of the metal strip and thus projects from at least one side of the overfolded member, and desirably projects from each side. A plurality of such core members are gathered together, and a binder, e.g., a ring or rings placed about the projecting end or ends so that the rods or bars form a central core with the balance of the thin metal strips extending outwardly therefrom. This assembly is then enclosed in a peripheral housing member, e.g., a ring or an oval. Desirably, the housing has an internal dimension (or dimensions) from the central core to peripheral housing less than the normal radial extension of the core portions whereby the core members may be compressed into a more nearly uniform cell density across the gas intercepting face. In the case of a ring-form housing, it has an internal diameter measured from the central circular core which is less than the unflexed extension of the core member portions. Thus, in the case of a ring or circular housing so dimensioned, it is convenient to wind spirally the assembly of core members about the central core to fit within the housing. It is also convenient to weld tabs fastened to or integral with the free ends of the corrugated thin metal strip portions directly to the housing. A voltage source, e.g., a 12 volt battery, may be attached, one pole to the central core, and the other to the housing to enable electrical heating of the converter body. The foregoing assembly is then placed in a suitable housing for insertion in the exhaust line from an internal combustion engine.